Bicycles have been used for transportation for many years. Recently, bicycles have been increasingly utilized for exercise and health reasons. A such, there are many different types of bicycles for different purposes such as racing, traversing unpaved train and touring.
Many bicycles include multi-speed transmissions to enhance their operation over different types of train. Existing bicycle transmissions are generally derailleur type, manually controlled by a cable connected to a shift lever. Moving the shift lever changes the cable tension and moves the derailleur and a drive chain from one gear to another gear. With different gearing ratios, different pedaling efforts and speeds are accomplished.
A disadvantage of such transmissions is that shifting gears cannot be accomplished without rotation of the gears. As such, proper gear shifting can only be performed when the bicycle is in motion, and a rider cannot shift gears when stopped. This is particularly problematic in cases where before stopping the bicycle transmission has been shifted to higher gears for high speed travel. Then when the rider stops, the rider must exert a large amount of pedaling force to start the bicycle moving again. Since the transmission requires rotation of the transmission gears by a forward motion of the bicycle, the rider cannot down shift the transmission to reduce the pedaling effort required to start the bicycle moving again.
Another disadvantage of such conventional transmissions is that the gears are exposed to the elements and road dirt, leading to premature wear and requiring frequent maintenance.
There is therefore a need for a multi-speed transmission for a bicycle which can be shifted while the bicycle is stationary. There is also a need for such a transmission to require infrequent maintenance without premature wear and tear.